1. Field of the Invention
This invention relates generally to door locks or sliding doors and other closures and more particularly to a door lock for selectively sccuring a door in its fully closed position and in a partially open position.
2. Prior Art
As it will appear from the ensuing description, the door lock of the invention may be used on a variety of doors and other closures. However, the invention is particularly designed for use on sliding patio doors and, for this reason, will be described in this context. Accordingly, it should be understood at the outset that the expression door, sliding door, and the like arc used in this disclosure in a broad sense to cover closures generally including windows, access doors, patio doors, and the like.
It is common practice to provide dwellings having patios, garden areas, and the like with sliding glass doors which open to these areas. Such sliding doors provide a large door opening and a large glass area which admits much light and ventilation to the adjacent room and provides an excellent view of the outside area.
Sliding patio doors of this kind may be left in any one of three positions. These positions are a fully closed position, a partially open position, and a fully open position. A wide variety of door locks have been devised for securing sliding patio doors in their fully closed position. One such lock is described in my U.S. Pat. No. 4,378,684, entitled "Double Cylinder Sliding Door Lock." There is no need, of course, to secure a sliding patio door in a fully open position. It is often desirable, however, to lock a sliding patio door in a partially open position which provides ventilation to the adjacent room while preventing entrance by an intruder.
A variety of door locks have been devised for securing both sliding and swinging doors in a partially open position. Examples of such door locks are bars which are placed in the sliding door track behind the sliding door panel, stops which are clamped to the trap door chains, and the like.
While these latter door locks provide the desired security in preventing further opening of a partially open sliding door, the locks suffer from certain disadvantages. One disadvantage is that they are completely separate from the main door lock which secures the door in its fully closed position. Locks of this type, therefore, require separate installation and operation of both the main door lock and the lock for securing the door in its partially open position. A disadvantage of the track mounted sliding door is that they are difficult to reach located, as they are, along the bottom track of the sliding door panel. Further, at least some of the existing locks must be completely removed and stored when not in use, which in inconvenient. Accordingly, there is a need for an improved sliding door lock which permits convenient locking of a sliding patio door, and the like, in both its fully closed position and a partially open position without requiring separate installation and operation of the closed and partially open lock components or storage of one lock component when not in use.